Calcite

1. Calcium carbonate (CaCO3). 2. A trade name for finely ground grades of marble or limestone, very high in calcium carbonate, which are used to raise the pH reading (reduce the acidity) of low pH (acidic) water or to filter out sediment. See Also: Hardness as Calcium Carbonate Calcium Carbonate Carbonate Hardness Bicarbonate Hardness Hardness Hardness as Calcium Carbonate Plastic Pipe Calcium Carbonate Total Hardness (TH) Soda Ash